The eastern basin of Long Island Sound ranks high for water quality, as it benefits from lower population density in the region and natural tidal flushing from the ocean, according to the 2020 Long Island Sound Report Card released this past week by Save the Sound.

The eastern basin earned an “A+” grading in the water quality report card, which is released every two years, while western parts of the Sound, which face higher population density and less natural flushing from the ocean, fared worse, said Peter Linderoth, director of water quality for Save the Sound.

This year, the report not only graded the open water of the Sound, but also the water quality of 50 bays and bay segments to call attention to high-priority areas for restoration efforts, as well as areas that deserve continued protection, he said.

Southeastern Connecticut is home to some of the highest graded locations in the state — Outer Stonington Harbor, Mystic Harbor, Outer Niantic River and Inner Stonington Harbor — but also one of the lowest, with Wequetequock Cove receiving a “D-" grade.

The grades for the region are as follows:

Wequetequock Cove: D-

Mystic River: B

Mystic Harbor: A

Inner Stonington Harbor: A-

Outer Stonington Harbor: A

Alewife Cove: B

Inner Niantic River: B

Outer Niantic River: A-

Connecticut River: B+

The water quality in neighboring Long Island Sound doesn't predict the water quality in a single bay, because the “shallow bays are impacted by the human-sourced pollution flowing in with their local freshwater,” said Jamie Vaudrey, assistant research professor in the Department of Marine Sciences at the University of Connecticut and one of the science advisers on the Unified Water Study working on the grading system and the report card.

“When coupled with poor tidal flushing due to restrictions like train bridges and sand bars, the water quality in these bays can be worse than in the main stem of the Sound,” she said. “This is evidenced by the poor grade we see in Wequetequock Cove, located in the Eastern Sound.”

Overall, the bays in the eastern Sound scored “quite well, reflecting the lower population density and greater amount of undeveloped space in this end of the Sound,” Vaudrey said.

However, the overall report of 50 bays and bay segments in Long Island Sound found that less than half of them earned a B or higher grade, and the report raises concerns “about the current ecological health of local bays and their resilience in the face of warming trends and ongoing pollution from Sound communities,” according to a news release from Save the Sound.

Save the Sound also points out in the release that 48% received poor grades for dissolved oxygen levels: low levels can result in fish and marine life die-offs.

Linderoth said climate change and excess nitrogen are major challenges to water quality. People can learn more about each bay at soundhealthexplorer.org and see action steps they can take.

The Wequetequock Cove watershed, for example, has a lot of septic systems, so ensuring they are working properly, and, if possible, upgrading to infrastructure with more advanced technology to treat nitrogen would go a long way to improving water quality, Linderoth said.

The cove also has limited natural flushing of the water due to train tracks in the area, Fran Pijar said, co-chair for water monitoring for Clean Up Sound and Harbors, the local organization that collected the data for Wequetequock Cove, Mystic River and Mystic Harbor.

Reducing fertilizer applications in the watershed and infiltrating stormwater into the ground with green infrastructure are also important steps to improve water quality, Linderoth said.

Pijar recommends plantings along the water’s edge so stormwater is captured by them rather than running directly into the water.

Local efforts

Pijar said the report card provides a way to look at what is happening to water quality of the entire Sound and through the bays. The document identifies where there are issues and where there is healthy water and shows that there are opportunities to improve water quality.

For its analysis, Save the Sound used open water data from the Connecticut Department of Energy and Environmental Protection, New York City Department of Environmental Protection, and the Interstate Environmental Commission, Linderoth said.

For the bays and harbors, 22 monitoring groups collected the data under a water quality monitoring program funded by the Environmental Protection Agency Long Island Sound Study, he said.

Fred Grimsey, founder and president of Save the River-Save the Hills, said he remembers that the water quality in the Niantic River is starkly different from what it was in the early 2000s.

“Our good scores in this year’s report reflect multiple factors: the natural filtering of nitrogen that the undeveloped Oswegatchie Hills coastal forest in East Lyme provides; sewers installed about 10 years ago in Pine Grove community below Smith Cove in Niantic Village, and the pump-out boat program that provides free removal of human sewage waste from pleasure boats on the Niantic each summer and fall,” he said.

Jordan Slocum, registrar of the New England Science & Sailing Foundation, which collected data for Stonington Harbor and Alewife Cove, said it’s important to “have this data available to educate the public on the health of our waterways and the impact that each one of us has on it.”

“Stonington Harbor has received an A on the report card, but the lower grades observed in neighboring areas should remind us not to take it for granted,” Slocum said. “It is up to all of us to keep our waters clean and healthy.”

Angela Chaffee, communications director for the Connecticut River Conservancy, which collected the data for the Connecticut River, said the river contributes to 70% of the fresh water entering Long Island Sound so the organization’s goal is to keep the water as clean as possible. The organization not only focuses on the mouth of the river near the Sound, but also works across all four Connecticut River states.

“We work with partners on all levels to collect and test water samples, find and fix pollution hot spots,” she said. “Clean rivers are so important, contributing to healthy communities and healthy economies.”

k.drelich@theday.com